Differential feed mechanism for a sewing machine

ABSTRACT

A differential feed mechanism is provided for a high-speed industrial sewing machine. The differential mechanism includes separate driving mechanisms for each of two feed dogs mounted on feed bars, both mechanisms connected to the main drive shaft of the sewing machine. Separate adjusting means are provided in each of the feed dog driving mechanisms to adjust individually, rapidly and at will, the length of the horizontal feed stroke of each feed dog.

United States Patent Clarence C. Smith Chicago;

Henry Szostak, Oak Park, both of ill. 827,685

May 26, 1969 Oct. 1 2, 1 97 1 Union Special Machine Company Chicago,Ill.

Inventors App]v N0. Filed Patented Assignee DIFFERENTIAL FEED MECHANISMFOR A SEWING MACHINE 15 Claims, 10 Drawing Figs.

U.S. c1 74 40, 1 12 209 Int. Cl n05b2' F 1 6h 21 32 Field of Search112/162,

[56] References Cited UNITED STATES PATENTS 2,677,280 5/1954Geulemans... 74/40 2,711,144 6/1955 Jullie 1 121209 2,879,733 3/1959Pierce 112/162 3,202,121 8/1965 Orth et a1 1 12/209 3,3 68,507 2/1968Orth 1 l2/209 Primary Examiner-William F. O'Dea Assistant ExaminerWesleyS. Ratliff, J rv Att0rneyDonald E. Degling ABSTRACT: A differential feedmechanism is provided for a high-speed industrial sewing machine. Thedifferential mechanism includes separate driving mechanisms for each oftwo feed dogs mounted on feed bars, both mechanisms connected to themain drive shaft of the sewing machine. Separate adjusting means areprovided in each of the feed dog driving mechanisms to adjustindividually, rapidly and at will, the length of the horizontal feedstroke of each feed dog PATENTEDnnnzmz 31611817 SHEET 2 OF 5 lib"PATENTEU 0m 1 2197i 2.611.817

sum 3 0r 5 PATENTEU 0m 1 2 an SHEET U UF 5 PATENTED DU 1 2 |97| SHEET 5[1F 5 FIGS.

DIFFERENTIAL FEED MECHANISM FOR A SEWING MACHINE This invention relatesto industrial sewing machines and particularly to an overedge sewingmachine having an improved differential feed mechanism.

The differential feed mechanism of the present invention is particularlyuseful in connection with overedge sewing machines such as are disclosedin Wallenberg US. Pat. No. 2,704,042, issued Mar. 15, I955. Reference ismade to the Wallenberg patent for a description of the generalconstruction of a sewing machine adaptable to the present invention.

A principal object of the invention is to provide a simple, compact andsturdy sewing machine capable of operation at high speeds, e.g., 5,000to 6,000 or more stitches per minute without objectionable noise orvibration and in which the work feed mechanism is of the differentialtype having an improved means for imparting horizontal feed motion tofeed dogs carried on feed bars.

Another object of the invention is to provide a differential feedmechanism for an overedge sewing machine having provision for adjustingthe length of the feed stroke of each feed bar individually and in aprecise and controllable manner.

Still another object of the invention is to provide a differential feedmechanism for a sewing machine in which the driving connections from adrive shaft to each feed bar are separate from the others.

A feature of the present invention is the provision of a new andimproved differential feed mechanism having the two feed dogs carried onrespective feed bars arranged in side by side relation. Common mechanismis provide for both feed bars to impart vertical movements to the feeddogs. Separate driving mechanism is provided for each of the two feedbars for effecting horizontal movement. Similarly, separate feedadjustment means for individually adjusting the feed stroke length ofeach feed bar, independently from the other, is provided.

Another feature of the invention is the provision of adjusting means andcontrol means for quickly and intermittently varying the horizontal feedstroke of at least one of the two feed bars during operation of thesewing machine and providing a limit on the variation of the feed stroketo a preselected minimum and maximum which may be changed at the will ofthe operator at any time even during the operation of the sewingmachine.

Still another feature of the invention is the provision of differentialfeed mechanism having a pair of feed bars, a feed dog carried on each ofthe feed bars and driving means for each of the feed bars which compriseseparate connections, from the main drive shaft to each feed bar, inspaced relation to each other. In this way, the connections to one ofthe feed bars from the main drive is disposed within the enclosedhousing of the sewing machine frame while the connections to the otherof the feed bars is disposed in a feed mechanism compartment at the endof the sewing machine frame.

Another feature of the differential feed mechanism of the presentinvention is the space-saving characteristic. The mechanism forseparately adjusting the horizontal stroke length of each of the feedbars comprises a pair of crank means operable concentrically with anactuating shaft on which one of the two crank means is rigidly fixed andthe other loosely supported for carrying into effect the adjustment ofeach feed bar individually in response to a respective actuation ofmicrometer-type control means by the operator.

Finally, it is a feature of this invention to provide means forreturning lubricants from the feed mechanism through the hollow mainshaft to the enclosed housing of the machine frame. This means comprisesa felt pad arranged in the bottom portion of the feed mechanismcompartment, tubing means having one end communicating with the felt padand the other end opening into a bearing bushing which, in conjunctionwith the main shaft, functions as a pump due to the provision ofinternal spiral grooves in the bushing.

Other objects, features and advantages of the invention will appear fromthe following detailed description of an illustrative machine embodyingthe invention. In the accompanying drawings:

FIG. 1 is a front elevational view, partly in section, of a machineincorporating the present invention;

FIG. 2 is a side elevational view, partly in section, taken along line2-2 of FIG. 1;

FIG. 3 is a vertical sectional view of the differential feed mechanismshown in FIGS. 1 and 2 and taken substantially along the planes of line33 of FIG. 2;

FIG. 4 is a vertical sectional view of the differential feed mechanismand operating means therefor, taken along line 4-4 of FIG. I;

FIG. 5 is a horizontal sectional view, taken along the broken line 5-5of FIG. 2;

FIG. 6 is an exploded perspective view of the entire feed and feedadjusting mechanism;

FIG. 7 is a side elevational view of the operator actuated control meansfor adjusting the horizontal feed stroke of the auxiliary feed means.The mechanism shown in FIG. 7 appears at the left end of FIG. 1;

FIG. 8 is an enlarged fragmentary view of a portion of the feed controlmechanism, taken along the transverse plane of line 8-8 of FIG. 7;

FIG. 9 is a view of the operator actuated control means shown in FIG. 7;

FIG. 10 is a vertical sectional view taken substantially along line10-40 of FIG. 1 showing the driving connections for imparting horizontalmovement to the auxiliary feed bar.

Referring now to FIGS. I and 2 of the drawings, a sewing machine [0 isprovided with a main frame 11 having an enclosed housing Ila for themain operating portions of the machine. A top cover I3 of the frame [Iprovides a closure for the top of the frame and also serves to supportvarious devices, including thread-tensioning devices which, not beingrelevant to the present invention, are not shown in the drawings. Awork-supporting frame portion Ilb extends from the enclosed housing lla.A bottom closure plate [6 extends beneath the enclosed housing 11a andthe work-supporting frame portion 11b and provides a means forsupporting the machine from a suitable table or stand. Adjacent to itsleft end, as viewed in FIG. I, the bottom plate 16 contains an openingI7 which is closed by a plate 18. The plate [8 is provided with adownwardly bulging portion to accommodate parts of the feed mechanism tobe described hereinafter. A cloth plate 20 is positioned on top of thesupporting frame portion 11b and contains an imbcdded throat plate 2!.An arm 22 extends longitudinally from the top cover [3 at a suitabledistance above the cloth plate 20. Arm 22 serves as a support for springmeans acting upon a presser arm 25 which, in turn, carries a presserfoot 26. The stitch forming parts of the machine, so far as shown,comprise a curved needle 27 which is clamped to the head of an arm 28the other end of which is secured to rock shaft 29. As disclosed in theWallcnberg patent referred to above, the rock shaft 29 is arranged to herocked upon each revolution of the main drive shaft 30 of the machine.The needle 27 cooperates with upper and lower looper means which are notshown in the present drawings, since such looper means are disclosed inthe Wallenberg patent. Other details of the actual machine which are notshown, since they are disclosed in said patent, include a worktrimmingmeans disposed in advance of the zone in which the stitch-formingdevices serve to produce the overedge stitch.

Work is advanced to and through the region where the stitches are formedby means of a main feed dog 35 and an auxiliary or differential feed dog36 (see FIGS. 2, 4 and 6). The main feed dog 35 is mounted on theforward end ofa feed bar 37 while the differential feed dog 36 ismounted on a feed bar 38 which is adjacent and substantially parallel tothe feed bar 37. Preferably, the two feed dogs 35 and 36 are mounted ontheir respective feed bars 37 and 38 in such manner as to permit acertain amount of vertical adjustment thereof in relation to therespective bars, as for example, by the elongated holes 35a and 36aprovided in the feed dogs 35 and 36. Each feed bar 37, 38, is formedwith a rearward extension 37a, 380 which mates with a block 39 mountedfor free oscillation upon an eccentric portion 410 of an adjustable pin41 received in the rear wall of the frame portion llb (FIG. Lateralmovement of the feed bars 37 and 38 is prevented in one direction by awasher 42 which seats against a collar 41b of the pin 41 and in theother direction by an abutment surface 43a of a stud 43 which isadjustably received in another portion of the rear wall of the frame llb(see FIGS. 5 and 6). The pin 41 may be rotated to vary the elevation ofits eccentric portion 410 and locked into any desired position bysetscrew 44. It will be seen that the feed bars 37 and 38 thus willpivot around the axis of the eccentric 41a and slide upon the block 39in a longitudinal direction. The location of the axis of the eccentric410 will thus determine, in part, the path of movement of the feed dogs35 and 36.

As shown most clearly in FIG. 6, the feed bars 37 and 38 are notidentical in shape. Feed bar 37 is provided at its forward end with adownwardly and fonvardly extending forked portion 37!: which is spacedapart from the upper forward end 37c of the feed bar. In contrast, feedbar 38 contains no fork at its forward end but terminates in a squareend 38bv The forwardly extending forked portion of the feed bar 37cooperates in sliding relationship with a block 45 mounted on aneccentric portion 300 of the main drive shaft 30. As best shown in FIG.I, the drive shaft 30 is mounted for free rotation in bearings 50received in the frame 11c of the enclosed housing lla. It will be seenthat rotation of the main drive shaft 30 will cause the block 45 to movein a circular path and impart a rising and falling motion to the forwardend of the feed bar 37. As the block 45 slides in the forked portion ofthe feed bar 37 it will impart no forward or rearward motion to the feedbar. As best shown in FIG. I, a flat portion 37d extends laterally fromthe main feed bar 37 and engages the flat undersurface 38c of-thcauxiliary feed bar 38. Thus, while feed bar 38 may slide longitudinallyrelative to feed bar 37 it is constrained to movein a vertical directionalong with feed bar 37. In addition to the lateral extension 37d, feedbar 38 is provided with a longitudinal guide slot 38d intermediate itsends. A slide block 51 cooperates with the guide slot 38d. The slideblock 51 is carried by a screw stud 52 extending through a suitable hole37a in the main feed bar 37. In order to prevent relative lateralmovement between the main feed bar 37 and the auxiliary feed bar 38, theslide block 51 is formed with angled faces converging toward the feedbar 37 and the guide slots 38d are formed with mating slanted surfaces.It may therefore be seen that the auxiliary feed bar 38 is constrainedto move in a vertical direction with the feed bar 37 but is free to movelongitudinally independently of the feed bar 37.

Having now described the means for providing vertical motion to the mainfeed bar 37 and auxiliary feed bar 38, the means for impartingreciprocal horizontal motion independently to each of the two feed barswill now be described.

Horizontal reciprocal motion is imparted to each of the two feed bars 37and 38 by its own drive through the respective eccentrics 55, 56provided in spaced relation on the main drive shaft 30. As best shown inFIG. 6, the eccentric 55 is carried on a reduced eccentric portion 30bof the drive shaft 30. The eccentric 55 is fastened to the eccentric 30bby a key 54 which is seated in the key way 30c. The eccentric 55 may beof any suitable throw for varying the extent of the horizontal movementimparted to the main feed bar 37. The eccentric 55 cooperates with onestrap portion 600 of a pitman 60. The other strap portion 60b of thepitman 60 engages the eccentric hub portion 61a ofa bushing 61 which is,in turn, received on a screw stud 62 extending through a bore 64b in thesegmental portion 640 of a rocker 64. The bushing 61 is clamped on thescrew stud 62 by a lock nut 65. It will be appreciated that rotation ofthe bushing 61 in the strap portion 60b of the pitman 60 will increaseor decrease the horizontal distance between the rocker 64, andultimately the main feed bar 37, with respect to the frame of themachine and the auxiliary feed bar 38. The bushing 61 can, of course, beadjusted to any desired position and then locked in that position. Toinsure that the position of the bushing 61 cannot be changed once it hasbeen adjusted to the desired position, a lock pin 66 is provided whichengages with a notch 67 in the head of the screw stud 62 and an orifice68 provided in the rocker 64 adjacent the studreceiving hole 64b. Therocker 64 is rotatably journaled upon a shaft 70 which, in turn, isrotatably journaled in bearings 7| received in the rearward portion ofthe frame I] (see FIG. 3).

As shown in FIGS. 2 and 3, the segmental portion 640 of the rocker 64extends perpendicularly to the axis of the shaft 70 and in a generallyupward direction from the shaft 70. It is formed with an arcuate slot64c within which a block 72 slides. Block 72 is journaled on the outerreduced diameter portion 73a of a hub provided in the rearward end 740of a link 74. The block 72 is affixed to the hub 730 by a screw 75threaded into the hub 730. At its forward end, link 74 is provided witha strap portion 74b which rotatably encompasses a bearing sleeve 76received on a screw stud 79. Screw stud 79 passes through a bore in themain feed bar 37 and is constrained against rotary movement in the feedbar by a lock pin 66 similar to that described above in connection withthe screw stud 62. Axial movement of the link 74 on the bearing sleeve76 is prevented by a lock nut 69 shown in FIG. 5. Lock nut 69 istightened against the side face of the bearing sleeve 76 but does notinhibit rotation of the link 74 on the bearing sleeve 76. With referenceto FIGS. 2 and 6, it will be seen that the link 74 is disposed in agenerally horizontal direction extending forwardly of its connection at74a with the slide block 72. The large diameter, shoulder portion 73b ofthe hub 73 rotatably carries the upper end 770 of a generally verticallydisposed curved arm 77. The lower end 77b of the arm 77 is pivotallyconnected to the free end of an arm 78a of crank member 78. Theconnection between arm 77 and crank 78 is formed with a screw stud 96and a bushing nut 94. Crank member 78 contains a sleeve portion 781)which is journalcd on a rock shaft 80 which is parallel with rock shaft70 and main shaft 30 and disposed below both of those shafts.

Rack shaft 80 is journaled for rotary movement in frame 111) of themachine in suitable bearings 81 and 87!) at points adjacent the ends ofthe shaft. Referring to FIG. I, it will be seen that a portion 800 ofthe rock shaft 80 extends outwardly from the machine frame H17 andthrough an indicia plate 85. lnwardly of the indicia plate 85 rock shaft80 carries an indicating member 87 including an indicating finger 87aand the sleeve bearing 87b. Sleeve hearing 87!; is rotatably received ina bearing 88 in the frame portion 11b and, as noted above, serves as abearing for one end of the shaft 80. A differential feed adjustmentlever 86 is fastened to the protruding end 800 of the rock shaft 80. Thefunction and operation of lever 86 will be discussed hereinafter.

As shown in FIGS. 1 and 6, a pair of dogs 87c are formed on the rightend of the sleeve bearing 87b. The dogs 87c engage with grooves 780formed in the left portion of the sleeve 78b. By virtue of the dogs 87cand the grooves 78c the indicating member 87 is secured to the crankmember 78 and both turn together on the rock shaft 80. As will becomeclear hereafter, both the crank member 78 and the indicating member 87are constrained from axial movement along the rock shaft 80. Movement tothe left as viewed in FIG. I is prevented by the abutment of the sleeve87b against the indicia plate 85. At the right of crank 78 is a sleeve90 which is rotatably carried on the rock shaft 80. Axial movement ofthe sleeve 90 is prevented by the crank 91 which is secured to the shaft80 and abuts against the right edge of the sleeve 90.

The feed stroke adjusting means of the differential feed mechanism isnormally urged into such a position that it causes the driving means toimpart a minimum stroke to the feed bars. This is accomplished with atorsion spring 92, preferably of the coil type, which is received on thesleeve 90. The torsion spring 92 comprises a pair of outer arms 92a and92b and an inner arm 92c. The outer arms 92:: and b comprise the twoends of the spring wire while the inner arm 920 is a loop formed fromthe center of the coil of wire. The arms 921i ltllOllS Oi) l 2 and b ofthe torsion spring 92 act on the cranks 78, 9I and urge the respectivecrank arms 78a and 9I in a downward direction. The inner loop 92c of thespring 92 is engaged by a screw 93 which is threaded into the rearwardlyfacing wall of the internal frame portion of the machine (see FIG. 4).As noted above, with the central portion of the spring 92 held fast, thearms 92 a and b exert a downward bias on the cranks 78a and 91. As shownmost clearly in FIG. 1, arm 92a acts against the shoulder of the bushingnut 94 which is connected to the arm 78a of the crank 78 while arm 92bof the spring 92 acts against a similar bushing nut 95 which is fastenedto the crank 9I by a stud screw 97. Screw 97 and bushing nut 95 alsoprovide a pivotal connection for the lower end of curved arm 98 as isbest shown in FIGS. 2 and 4. The motion of the crank arms 78a. 9| issuch that in one extreme position they pass through the orifice I7 inthe bottom plate 16 of the sewing machine. To accommodate this movementof the cranks a bulged plate I8 has been provided.

As stated above, arm 98 is connected at its lower end to crank 9I. Atits upper end the arm 98 is pivotally connected to a slide block I00 atthe forked end 1100 of a link 110 through a connecting pin III. Theinterconnection of the arm 98, link I and slide block 100 is made fastby a setscrew 100a threaded into the slide block 100 and acting againstthe side of the pin III. Slide block 100 is arranged to slide in theslot I0lb of the rocker 101 which is rigidly secured to the rock shaft70.

Consideration of the rocker I01 and its connection to the arm 98 and thelink I10 reveals that as the slide block 100 is moved in the slide IOIbby the action of the crank 91 and the arm 98, a shift of the slide blockI00 up or down will correspondingly increase or decrease the horizontalmovement of the arm 110 which movement will be transferred to theauxiliary feed bar 38 as hereinafter explained. The action justdescribed with respect to the rocker 10I is generally similar to theaction of rocker 64 which is freely journaled on the shaft 70. Upward ordownward movement of the block 72 will respectively increase or decreasethe horizontal movement imparted to the link 74 which is connected tothe main feed bar 37. It will now be understood that the effect of thedownward bias of the spring arms 92a and 92b of the torsion spring 92acting on the cranks 78 and 9] will be to move the slide blocks 72 and100 to their lowest positions and correspondingly impart a minimum feedstroke to each of the feed bars 37 and 38.

Turning now to the driving mechanism for the auxiliary feed bar 38, itwill be understood from FIGS. 3, 4 and 6 that the auxiliary feed bar 38receives its horizontal motion from the main shaft 30 through the rockshaft 70. The latter shaft is placed in oscillating motion by the pitmanI02 disposed in the interior of the enclosed housing Ila (see FIG. 5).The pitman 102 is provided with a strap portion 1020 on the forward endand a strap portion l02b on its rearward end. The strap portion I020 ofpitman 102 is joumaled on the eccentric 56 of the main drive shaft 30while the strap portion [02b is journaled on a pin I03 pivotallyreceived in appropriate hearings on a yoke 1040 of a crank lever 104.Crank lever 104 is rigidly secured to the rock shaft 70. Thus, rotationof the main drive shaft 30 will place rock shaft 70 into an oscillatingmotion. It is clear that the amplitude of the oscillating motion of rockshaft 70 will depend upon the throw of the eccentric 56 as well as thelength of the lever I04. The effective length of the crank lever I04 maybe changed by changing the location of the pin I03 relative to the axisof the rock shaft 70. Accordingly, the crank lever 104 may be designedwith two sets of bearing holes I05 and I06 to provide an adjustment inthe degree of oscillation of the rock shaft 70. Pin I03 is constrainedagainst axial movement in either set of bearing holes by its rigidconnection with the strap portion I02b of the pitman 102. This rigidconnection is provided by a setscrew I07 threaded into the strap portion102k and acting against the pin 103.

Referring to FIG. 6, it will be clear that oscillation of the rock shaft70 causes a corresponding oscillation of the rocker 101. Motion of therocker It" is transmitted via the link IIO to the forward end of theauxiliary feed bar 38 in the following manner: The forward strap portionIIOb of the link IIO is journaled on a bushing 112 which is, in turn,mounted on a screw stud I13 projecting from the right-hand side of theauxiliary feed bar 38 as viewed in FIG. 6. The screw stud H3 is receivedin a suitable bore I14 formed in the auxiliary feed bar so that at theleft side of the feed bar 38 the head portion of the stud 113 will beflush with the side surface of the feed bar. To constrain the stud 113against rotary movement in the bore 114 a lock pin similar to the lockpin 66 cooperating with the screw stud 62 is provided. The screw studII3 is connected through the sleeve 112 and strap IIOb by a lock nut II5.

Having now completed the description of the drive mechanism for thehorizontal and vertical motions of the feed bars it will be appreciatedthat though both feed bars 37 and 38 are driven from the same main driveshaft 30, the drive trains from that shaft are substantially independentand each drive train may be adjusted insofar as the horizontal feed isconcerned independent of the other.

We turn now to the control means for adjusting the feed stroke of thefeed bars. Adjustment of the feed stroke of the main feed bar 37 isaccomplished by turning the adjustment rod 120 clockwise orcounterclockwise as may be desired. Adjustment rod 120 is threaded intoa suitable bore l2I in the frame portion 11b of the machine. The boreI2I, as is most clearly shown in FIG. 2, extends downwardly andrearwardly toward and below the rock shaft and is directed toward a nose78d projecting downwardly from the sleeve 78b of crank member 78.Clockwise rotation of the rod I20 will cause the rod to move inwardlyand, in engaging nose 78d of crank member 78, will cause the crankmember to be rotated on the rock shaft 80 against the force of thetorsion spring 92. In like manner, counterclockwise rotation of theadjustment rod 120 will result in withdrawing the adjustment rod fromthe bore and permitting the crank 78 to rotate in a counterclockwisedirection. The adjustment rod 120 is provided with a knurled knob I201:for convenience of operation. Clockwise rotation of the adjustment rod120 will increase the horizontal feed stroke of the main feed bar 37while counterclockwise rota tion of the adjustment rod I20 will reducethe horizontal feed stroke of the main feed bar 37. To prevent theadjustment rod 120 from completely disengaging the nose 78d of the crank78, a C washer 122 is fitted into an annular groove on the adjustmentrod. The C washer will abut against an internal portion of the frame IIb and thus limit the counterclockwise rotation of the adjustment rodI20. It is also desirable to provide locking means for the adjustmentrod I20. Such means include a lock pin I23 and a setscrew I24. Thesetscrew 124 is threaded into the frame IIb and forces the lock pin 123against the threaded portion of the adjustment rod 120 therebypreventing rotation of the adjustment rod in the bore I21 (see FIG. 2).

It will be recalled that the indicating arm 87b attached to the sleevebearing 87b is also interconnected with with the crank 78 through thedogs 87c and the grooves 78c. Thus, as the crank arm 70 is rotated ineither direction by means of the adjustment rod 120, the sleeve 87b andthe pointer 870 are constrained to rotate in unison with the crank 78.The location of the indicator finger 87a along the side face of theindicia plate will therefore give a measure of the length of thehorizontal feed stroke to which the mechanism has been adjusted byactuation of the adjustment rod I20. The actual length of the horizontalfeed stroke in terms of stitches per inch or any other convenientmeasure may be inscribed on the edge of the indicia plate 85 as shown inFIGS. 5 and 6v It will be appreciated that the use of a screw adjustmenton the adjustment rod provides a micrometer type of adjustment in thefeed length of the main feed bar 37 and hence a very precise control ofthe main feed bar.

A similar type of control is provided for the auxiliary feed bar 38. Theadjustment in this case comprises two basic settings, a maximum and aminimum setting. The minimum or normal setting provides for a minimumfeed stroke of the auxiliary feed bar while the maximum setting providesfor a maximum feed stroke. As the minimum feed stroke of the auxiliaryfeed bar can be smaller than the feed stroke of the main feed bar astretching of the material during the feeding action can be achievedwhile, on the other hand, the maximum setting of the auxiliary feed barcan be equal to the feed stroke length of the main feed bar in whichcase no differential feeding would be transacted during the activationof the maximum setting. If desired, however, the minimum feed stroke ofthe auxiliary feed bar could be made to match with the feed stroke ofthe main feed bar while the maximum feed stroke could be increased tocause shirring or gathering of the material. Of course, many variationsof the relationship between the two feed stroke lengths of the auxiliaryfeed bar and the one feed stroke length of the main feed bar can bebrought about by ad justing the feed stroke length of either one or theother of the two feed bars.

The control means for the feed adjusting mechanism for the auxiliaryfeed bar 38 comprises a mechanism for setting the minimum feed strokeand a mechanism for setting the maximum feed stroke. These adjustmentmeans are shown in FIGS. 6, 7, 8 and 9 and include a pair of concentricscrew elements comprising an inner rod 130 and an outer sleeve memberI3] slidably received on the rod I30. Rod I30 is journaled in a pair oflobes or flanges 85b which extend at right angles to the indicia plate85. The bearing lobes 85b are so arranged that the rod I30 is carried inan oblique direction more or less parallel to the adjustment rod 120.The rear end of the rod I30 carries a threaded sleeve I30b while aknurled knob I300 is secured to the forward end of the rod 130. Both theknurled knob 130a and the sleeve I30b are secured to the rod I30 so thatthey will rotate with the rod under all circumstances. A lower stopblock 132 is threaded on to the sleeve l30b of the rod I30. Stop blockI32 is provided with a flat face closely spaced from the indicia plate85 so that the stop block I32 will not rotate with the rod I30 but isconstrained to move axially relative to the rod I30 when that rod isrotated. As is best shown in FIGS. 6 and 7, the stop block 132 acts tolimit the counterclockwise rotation of the adjustment lever 86 whichoscillates on the end 800 of rock shaft 80. The adjustment arm 86 is inthe form of a bellcrank having arm 86a extending generally upwardly fromthe shaft 80 and arm 86b extending forwardly from the shaft 80. Anelongated slot is provided in the arm 860 through which the rod 130 mayextend.

As described above, the rock shaft 80 is biased on a coun terclockwisedirection by the torsion spring 92. Thus, the arm 86a of the bellcrank86 is biased in a counterclockwise direction into engagement with thestop block I32. As the counterclockwise extreme position of the rockshaft 80 determines the minimum horizontal feed of the auxiliary feedbar 38 it will be apparent that the adjustment of the minimum feed ofthe auxiliary feed bar 38 is controlled by the setting of the stop blockI32. For convenience of operation, the arm 86a of the bellcrank 86 alsofunctions as a pointer which cooperates with a scale inscribed on theside of the indicia plate 85. Since the adjustment of the bellcrank 86is performed by a screwthreaded means acting through the stop block I32it is possible to have a micrometer-type adjustment of the minimum feedof the auxiliary feed bar 38.

From the discussion above, it will now be apparent that as the bellcranklever 86 is rotated in a clockwise direction against the force of thetorsion spring 92 the horizontal feed of the auxiliary feed bar will beincreased corresponding to the angular movement of the bellcrank 86 andthe rotation of the rock shaft 80. Rotation of the lever 86 about theaxis of shaft 80 may be accomplished by a treadle, knee press or othersuitable means connected with the arm 86b of the bellcrank 86, forexample, by a chain or rod.

The maximum length of the feed stroke of the auxiliary feed bar 38 iscontrolled by an extreme clockwise position of the bellcrank lever 86.As best shown in FIGS. 6, 7 and 8,

clockwise motion of the bellcrank 86 is limited by the position of thestop element I310 which forms a portion of the threaded outersleevemember 13! which is concentric with the rotatable rod I30. Adjustment ofthe stop member 1310 is provided through a knurled and threaded collarI35. which is loosely positioned in a slot I36 formed in the indiciaplate 85. The knurled collar is threaded on to the sleeve member 131 sothat rotation of the collar I36 causes the sleeve member 13I to moveaxially along the rod I30. Stop element 1310 is formed with a flatsurface adjacent the indicia plate 85 so that the stop member 131a andthe sleeve member I3] are constrained against rotation. Since bothadjustments of the auxiliary feed bar are screw actuated, adjustablemicrometertype settings are provided for both the auxiliary feed bar 38and the actual feed stroke length may be observed on the indicia plate85, Under certain circumstances, it may be desirable to provide a singlefixed position of the bellcrank 86 which is intermediate the minimum andmaximum positions of the crank so as to provide a single feed strokelength for the auxiliary feed bar 38. To accomplish this, there isprovided a bore 86c in the arm 86a of the bellcrank 86 which cooperateswith an elongated arcuate slot I40 in the indicia plate 85. The arcu ateslot is formed with a recessed shoulder around its periphery. A slideblock l4I having a threaded hole is movable in the arcuate slot 140.Lock screw I42 which passes through bore 86c of the arm 86a engages withthe threaded hole of the slide block I41. When screw I42 is tightened,the slide block I41 bears against the recessed shoulder of the illcuateslot 140 and secures the arm 86a at any desired position between thestop block I32 and the stop element I3Ia.

To prevent accidental movement of the adjustment of the minimum andmaximum positions of the bellcrank 86 by rotation of the collar I35 orthe knob I30a, there is provided a double leaf spring fastened to theindicia plate 85 by a screw I46. Each end of the leaf spring I45 isprovided with a small convex deformity which engages with the knurledsurface of the knobs I300 and the collar I35 to inhibit frce rotation ofthe knob and collar.

The indicia plate 85 and the adjusting mechanism for the auxiliary feedbar 38 contained thereon is spaced from the left-hand end of the machineas viewed in FIG. I by a spacer plate in order that sufficient room beprovided for free movement of the indicia arm 870.

As best shown in FIGS. 2 and 6, there is provided a compact guide meansfor the main feed bar 37. This guide means comprises a member I5] whichis secured to the vertical portion of the separating wall Ilc. The guidemeans 151 is formed with a pair of upstanding side portions I5Ia and bfor guiding therebetween the downwardly extending front portion 37b ofthe main feed bar. As best shown in FIG. I, the guide means 151 isadjacent one of the main bearings 50 which supports the main drive shaft30.

It has been pointed out above that the feed drive mechanism of thepresent invention is physically separated from the rest of the sewingmachine mechanism by the wall I Iv of the main frame. It thereforebecomes necessary to provide an arrangement for pumping lubricant fromthe feed mechanism compartment back to the enclosed housing Ila. Theouter main bearing 50 is lubricated by a wick (not shown) which isplaced in a bore 152 which extends through the frame portion IIc to theenclosure Ild (see FIGS. I and 4). A vent bore I53 opens between thehearing seats in wall He between the two bearings 50. 50.

To remove excess oil from the feed mechanism compartment, a felt pad I55is arranged in the bottom portion of the feed mechanism compartment.Tubing means I56 communicate between the felt pad I55 and a fitting I57threaded into a bore 158 provided in a further main bearing 50 locatedin the main compartment of the sewing machine. The fitting 157communicates with a spiral groove 160 provided on the inner surface ofthe bearing bushing. Rotation of the main drive shaft 30 in the bearing50 generates a pumping effect by which lubricant collected in felt padI55 is withdrawn through the IOIOOS 00H tubing means 156 and pumped viathe spiral groove 160 into the enclosed housing of the sewing machine.

Turning now to the operation of the difi'erential feed mechanismaccording to operator present invention, it will be understood that theoperator first adjusts adjustment rod 120 in a clockwise orcounterclockwise direction as may be required until the indicia am 870indicates on the indicia aux iliary 85 the correct and desired settingfor the feed stroke of the main feed bar 37. Next, the operator rotatesthe knurled knob 1304 to adjust the stop I32 until the desired minimumfeed stroke length of the auxiliary feed bar 38 is attained. Of course,this minimum feed stroke length may be less than, equal to, or morethan, the feed stroke length of the main feed bar. The operator thenadjusts the maximum feed length of the auxiliary feed bar by rotatingthe knurled collar 135. In order to determine the maximum feed strokelength of the auxiliary bar 38, it is necessary to rotate the arm 86clockwise on its axis so that it is restrained by the adjustable stop1310. At this point the knurled collar I35 may be rotated until thedesired adjustment is attained. If the particular sewing operation to beaccomplished does not require both a maximum and a minimum feed lengthfor the auxiliary feed bar but instead requires a fixed setting, thenthe operator will set the crank lever 86 to the desired position andtighten the screw 142 and slide nut 14! until the indicator on arm 860shows the desired feed stroke length. Where the auxiliary feed bar hasbeen adjusted for maximum and minimum setting the operator then is freeto move the bellcrank lever 86 by a treadle or chain or otherappropriate means as desired during the sewing operation to vary thefeed stroke length of the auxiliary feed bar 38.

While an illustrative embodiment of the invention has been disclosed inconsiderable detail and various modifications have been suggested above,it will be understood that other changes may be made in the constructionand arrangement of the several parts within the scope of the appendedclaims.

What is claimed is:

l. in a sewing machine having a frame and a main drive shaft, adifferential feed mechanism comprising first and second feed barsarranged side by side having feed dogs affixed thereto and supported forreciprocating movement rela tive to said frame, slide meansinterconnecting said first and second feed bars to permit relativehorizontal longitudinal movement of said bars and to prevent relativevertical movement of said bars, said slide means including a firstadjustable slide block means pivotally mounted on said frame andinterconnecting said first and second feed bars at one end thereof and asecond slide block means pivoted on one of said feed bars intermediatethe ends thereof and interconnected with slot means formed in the otherof said feed bars, eccentric drive means interconnecting said driveshaft and said first feed bar to effect simultaneous vertical movementof said first and second feed bars, first adjustable drive meansinterconnecting said drive shaft and said fist feed bar for effectingreciprocating horizontal movement of said first feed bar, secondadjustable drive means interconnecting said drive shaft and said secondfeed bar for effecting reciprocating horizontal movement of said secondfeed bar, each of said first and second adjustable drive means includingrocker means formed with an arm containing a guide slot and a blockslideable in said guide slot, first adjustment means communicating withsaid first adjustable drive means to vary the extent of reciprocatinghorizontal movement of said first feed bar by controlling the positionof the said block in the guide slot of said rocker and second adjustmentmeans independent of said first adjustment means communicating with saidsecond adjustable drive means to vary the extent of the reciprocatinghorizontal movement of said second feed bar by controlling the positionof the said block in the guide slot of said rocker.

2. A differential feed mechanism as described in claim 1 wherein saidsecond adjustment means includes adjustable stop means cooperating withlever means whereby the horizontal feed stroke of said second feed barcan be varied at will during operation of the sewing machine betweenpreselected minimum and maximum lengths.

3. A differential feed mechanism as described in claim 2 wherein saidfirst adjustment means includes an indicator which cooperates with ascale affixed to said frame to indicate the amplitude of the horizontalfeed stroke of said first feed bar and said second adjustment meansincludes an indicator which cooperates with said scale to indicate theamplitude of the horizontal stroke of said second feed bar.

4. A differential feed mechanism as described in claim 3 wherein saidfirst and second adjustment means are screw actuated to provide amicrometer control of the adjustment means.

5. A differential feed mechanism as described in claim 2 in which saidfirst and second adjustable drive means and said first and secondadjustment means are carried on parallel rock shafts, said firstadjustable drive means and said first adjustment means being carriedloosely on said rock shafts and said second adjustable drive means andsaid second adjustment means being secured to said rock shafts.

6. A differential feed mechanism as described in claim 5 wherein saidfirst adjustment means includes an indicator which cooperates with ascale affixed to said frame to indicate the amplitude of the horizontalfeed stroke of said first feed bar and the second adjustment meansincludes an indicator which cooperates with said scale to indicate theamplitude of the horizontal feed stroke of said second feed bar.

7. A difi'erential feed mechanism as described in claim 6 wherein saidfirst and second adjustment means are screw actuated to provide amicrometer control of the adjustment means.

8. In a sewing machine having a frame and a main drive shaft, adifferential feed mechanism comprising first and second feed bars havingfeed dogs affixed thereto and supported for reciprocating motionrelative to said frame, first and second eccentrics on said main driveshaft, first and second rock shafts journaled in said frame, a firstrocker jour naled on said second rock shaft and having a guide slotformed therein, a block slidable in said slot, a first connecting linkpivotally connected at one end on said first feed bar, said block beingpivoted on the opposite end of said first connecting link, a firstpitman journaled at one end on said first eccentric and adjustablyjournaled at the other end on said first rocker, a first spring-biasedcrank rotatably mounted on said first rock shaft and having an arm and adog extending therefrom, a first connecting arm pivotally connected atone end to said first crank and at the opposite end to said opposite endof said first connecting link, an adjustment rod axially adjustable tocooperate with said dog to limit the rotation of said first crank in onedirection so as to control the position of the block in said firstrocker and to vary the amplitude of the reciprocating motion transmittedto said first feed bar, a second crank secured to said second rockshaft, a second pitman pivoted at one end to said second crank and atthe opposite end rotatably journaled on said second eccentric, a secondrocker secured to said second rock shaft and having a guide slot formedtherein, a block slidable in the slot of said second rocker, a secondconnecting link pivoted at one end on said second feed bar and at theopposite end on said block in said second rocker, a third spring-biasedcrank secured to said rock shaft and having an arm, a second connectingarm pivotally connected at one end to said arm of said third crank andat the opposite end to said opposite end of said second connecting link,and a lever secured to said first rock shaft to control the positionthereof and the position of the block in said second rocker to vary theamplitude of the reciprocating motion transmitted to said second feedbar.

9. A differential feed mechanism as described in claim 8 wherein thelever secured to said first rock shaft is rotatable about the axis ofsaid rock shaft within limits defined by a first adjustable stoplimiting the rotation of said lever in one direction and a secondadjustable stop limiting the rotation of said lever in the oppositedirection.

10. A differential feed mechanism as described in claim 9 wherein thelever secured to said first rock shaft may be secured to said frame atany position between the extreme positions defined by said first andsecond adjustable stops.

lDlOOS DOIS it. A differential feed mechanism as described in claim 9wherein an indicating crank is journaled on said first rock shaft andconstrained to oscillate with said first crank to indicate the positionof said first crank and the amplitude of the reciprocating motiontransmitted to said first feed bar.

[2. A differential feed mechanism as described in claim 9 wherein thelever secured to said first rock shaft is provided with an indicatingpointer to indicate the position of said lever and the amplitude of thereciprocating motion transmitted to said second feed bar.

13. A differential feed mechanism as described in claim 10 wherein thelever secured to said first rock shaft is provided with an indicatingpointer to indicate the position of said lever and the amplitude of thereciprocating motion transmitted to said second feed bar.

14. A differential feed mechanism as described in claim it wherein thelever secured to said first rock shaft is provided with an indicatingpointer to indicate the position of said lever and the amplitude of thereciprocating motion transmitted to said second feed bar.

15. A differential feed mechanism as described in claim 8 wherein saidmain drive shaft is provided with a bushing hav ing spiral groovesfonned therein and tube means communicating between said spiral groovesof said bushing and the compartment within said frame containing saidfirst and second feed bars whereby lubricant supplied to the feedmechanism is withdrawn through said tube means and bushing forrecirculation through said feed mechanism.

IOIOOS 00H) UNITED STATES PATENT oFFlcE CERTIFICATE Q? CSRRECTIGN PatentNo.3,6ll,8l7 Dated October 12, 1971 Inventor) Clarence C. Smith andHenry szostak It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column L, line 39, "Rack" should be --RocK-- Column 6, line 55, "arm 87bshould be --a rm 87a.

Column 7', line +7, "on should be --in-- Column 8, line 8, 'collar 136"should be --collar 135-- Column 9, line change "operator" to the--Column 9, lines 7 and 8, "indicia auxiliary 85" should be --indiciaplate 85-- Column 9, line 53, fist" should be --first-- Signed andsealed this 25th day of April 1972.

(SEEY A L; to a:

EDWARD MoFLETCI-IERJR. ROBERT GOTTSCHALE Attesting; Officer Commissionerof Patents

1. In a sewing machine having a frame and a main drive shaft, adifferential feed mechanism comprising first and second feed barsarranged side by side having feed dogs affixed thereto and supported forreciprocating movement relative to said frame, slide meansinterconnecting said first and second feed bars to permit relativehorizontal longitudinal movement of said bars and to prevent relativevertical movement of said bars, said slide means including a firstadjustable slide block means pivotally mounted on said frame andinterconnecting said first and second feed bars at one end thereof and asecond slide block means pivoted on one of said feed bars intermediatethe ends thereof and interconnected with slot means formed in the otherof said feed bars, eccentric drive means interconnecting said driveshaft and said first feed bar to effect simultaneous vertical movementof said first and second feed bars, first adjustable drive meansinterconnecting said drive shaft and said fist feed bar for effectingreciprocating horizontal movement of said first feed bar, secondadjustable drive means interconnecting said drive shaft and said secondfeed bar for effecting reciprocating horizontal movement of said secondfeed bar, each of said first and second adjustable drive means includingrocker means formed with an arm containing a guide slot and a blockslideable in said guide slot, first adjustment means communicating withsaid first adjustable drive means to vary the extent of reciprocatinghorizontal movemeNt of said first feed bar by controlling the positionof the said block in the guide slot of said rocker and second adjustmentmeans independent of said first adjustment means communicating with saidsecond adjustable drive means to vary the extent of the reciprocatinghorizontal movement of said second feed bar by controlling the positionof the said block in the guide slot of said rocker.
 2. A differentialfeed mechanism as described in claim 1 wherein said second adjustmentmeans includes adjustable stop means cooperating with lever meanswhereby the horizontal feed stroke of said second feed bar can be variedat will during operation of the sewing machine between preselectedminimum and maximum lengths.
 3. A differential feed mechanism asdescribed in claim 2 wherein said first adjustment means includes anindicator which cooperates with a scale affixed to said frame toindicate the amplitude of the horizontal feed stroke of said first feedbar and said second adjustment means includes an indicator whichcooperates with said scale to indicate the amplitude of the horizontalstroke of said second feed bar.
 4. A differential feed mechanism asdescribed in claim 3 wherein said first and second adjustment means arescrew actuated to provide a micrometer control of the adjustment means.5. A differential feed mechanism as described in claim 2 in which saidfirst and second adjustable drive means and said first and secondadjustment means are carried on parallel rock shafts, said firstadjustable drive means and said first adjustment means being carriedloosely on said rock shafts and said second adjustable drive means andsaid second adjustment means being secured to said rock shafts.
 6. Adifferential feed mechanism as described in claim 5 wherein said firstadjustment means includes an indicator which cooperates with a scaleaffixed to said frame to indicate the amplitude of the horizontal feedstroke of said first feed bar and the second adjustment means includesan indicator which cooperates with said scale to indicate the amplitudeof the horizontal feed stroke of said second feed bar.
 7. A differentialfeed mechanism as described in claim 6 wherein said first and secondadjustment means are screw actuated to provide a micrometer control ofthe adjustment means.
 8. In a sewing machine having a frame and a maindrive shaft, a differential feed mechanism comprising first and secondfeed bars having feed dogs affixed thereto and supported forreciprocating motion relative to said frame, first and second eccentricson said main drive shaft, first and second rock shafts journaled in saidframe, a first rocker journaled on said second rock shaft and having aguide slot formed therein, a block slidable in said slot, a firstconnecting link pivotally connected at one end on said first feed bar,said block being pivoted on the opposite end of said first connectinglink, a first pitman journaled at one end on said first eccentric andadjustably journaled at the other end on said first rocker, a firstspring-biased crank rotatably mounted on said first rock shaft andhaving an arm and a dog extending therefrom, a first connecting armpivotally connected at one end to said first crank and at the oppositeend to said opposite end of said first connecting link, an adjustmentrod axially adjustable to cooperate with said dog to limit the rotationof said first crank in one direction so as to control the position ofthe block in said first rocker and to vary the amplitude of thereciprocating motion transmitted to said first feed bar, a second cranksecured to said second rock shaft, a second pitman pivoted at one end tosaid second crank and at the opposite end rotatably journaled on saidsecond eccentric, a second rocker secured to said second rock shaft andhaving a guide slot formed therein, a block slidable in the slot of saidsecond rocker, a second connecting link pivoted at one end on saidsecond feed bar and at the opposite end on said block in said secondRocker, a third spring-biased crank secured to said rock shaft andhaving an arm, a second connecting arm pivotally connected at one end tosaid arm of said third crank and at the opposite end to said oppositeend of said second connecting link, and a lever secured to said firstrock shaft to control the position thereof and the position of the blockin said second rocker to vary the amplitude of the reciprocating motiontransmitted to said second feed bar.
 9. A differential feed mechanism asdescribed in claim 8 wherein the lever secured to said first rock shaftis rotatable about the axis of said rock shaft within limits defined bya first adjustable stop limiting the rotation of said lever in onedirection and a second adjustable stop limiting the rotation of saidlever in the opposite direction.
 10. A differential feed mechanism asdescribed in claim 9 wherein the lever secured to said first rock shaftmay be secured to said frame at any position between the extremepositions defined by said first and second adjustable stops.
 11. Adifferential feed mechanism as described in claim 9 wherein anindicating crank is journaled on said first rock shaft and constrainedto oscillate with said first crank to indicate the position of saidfirst crank and the amplitude of the reciprocating motion transmitted tosaid first feed bar.
 12. A differential feed mechanism as described inclaim 9 wherein the lever secured to said first rock shaft is providedwith an indicating pointer to indicate the position of said lever andthe amplitude of the reciprocating motion transmitted to said secondfeed bar.
 13. A differential feed mechanism as described in claim 10wherein the lever secured to said first rock shaft is provided with anindicating pointer to indicate the position of said lever and theamplitude of the reciprocating motion transmitted to said second feedbar.
 14. A differential feed mechanism as described in claim 11 whereinthe lever secured to said first rock shaft is provided with anindicating pointer to indicate the position of said lever and theamplitude of the reciprocating motion transmitted to said second feedbar.
 15. A differential feed mechanism as described in claim 8 whereinsaid main drive shaft is provided with a bushing having spiral groovesformed therein and tube means communicating between said spiral groovesof said bushing and the compartment within said frame containing saidfirst and second feed bars whereby lubricant supplied to the feedmechanism is withdrawn through said tube means and bushing forrecirculation through said feed mechanism.